1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
4 *
5 * Copyright (C) 2008 Mercury IMC Ltd
6 * Written by Mark Jackson <mpfj@mimc.co.uk>
7 *
8 * NOTE: Currently this driver only supports the bare minimum for read
9 * and write the RTC. The extra features provided by the chip family
10 * (alarms, trickle charger, different control registers) are unavailable.
11 */
12
13 #include <linux/init.h>
14 #include <linux/module.h>
15 #include <linux/platform_device.h>
16 #include <linux/rtc.h>
17 #include <linux/spi/spi.h>
18 #include <linux/bcd.h>
19 #include <linux/slab.h>
20 #include <linux/of.h>
21
22 #define DS1390_REG_100THS 0x00
23 #define DS1390_REG_SECONDS 0x01
24 #define DS1390_REG_MINUTES 0x02
25 #define DS1390_REG_HOURS 0x03
26 #define DS1390_REG_DAY 0x04
27 #define DS1390_REG_DATE 0x05
28 #define DS1390_REG_MONTH_CENT 0x06
29 #define DS1390_REG_YEAR 0x07
30
31 #define DS1390_REG_ALARM_100THS 0x08
32 #define DS1390_REG_ALARM_SECONDS 0x09
33 #define DS1390_REG_ALARM_MINUTES 0x0A
34 #define DS1390_REG_ALARM_HOURS 0x0B
35 #define DS1390_REG_ALARM_DAY_DATE 0x0C
36
37 #define DS1390_REG_CONTROL 0x0D
38 #define DS1390_REG_STATUS 0x0E
39 #define DS1390_REG_TRICKLE 0x0F
40
41 #define DS1390_TRICKLE_CHARGER_ENABLE 0xA0
42 #define DS1390_TRICKLE_CHARGER_250_OHM 0x01
43 #define DS1390_TRICKLE_CHARGER_2K_OHM 0x02
44 #define DS1390_TRICKLE_CHARGER_4K_OHM 0x03
45 #define DS1390_TRICKLE_CHARGER_NO_DIODE 0x04
46 #define DS1390_TRICKLE_CHARGER_DIODE 0x08
47
48 struct ds1390 {
49 struct rtc_device *rtc;
50 u8 txrx_buf[9]; /* cmd + 8 registers */
51 };
52
ds1390_set_reg(struct device * dev,unsigned char address,unsigned char data)53 static void ds1390_set_reg(struct device *dev, unsigned char address,
54 unsigned char data)
55 {
56 struct spi_device *spi = to_spi_device(dev);
57 unsigned char buf[2];
58
59 /* MSB must be '1' to write */
60 buf[0] = address | 0x80;
61 buf[1] = data;
62
63 spi_write(spi, buf, 2);
64 }
65
ds1390_get_reg(struct device * dev,unsigned char address,unsigned char * data)66 static int ds1390_get_reg(struct device *dev, unsigned char address,
67 unsigned char *data)
68 {
69 struct spi_device *spi = to_spi_device(dev);
70 struct ds1390 *chip = dev_get_drvdata(dev);
71 int status;
72
73 if (!data)
74 return -EINVAL;
75
76 /* Clear MSB to indicate read */
77 chip->txrx_buf[0] = address & 0x7f;
78 /* do the i/o */
79 status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
80 if (status != 0)
81 return status;
82
83 *data = chip->txrx_buf[0];
84
85 return 0;
86 }
87
ds1390_trickle_of_init(struct spi_device * spi)88 static void ds1390_trickle_of_init(struct spi_device *spi)
89 {
90 u32 ohms = 0;
91 u8 value;
92
93 if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
94 &ohms))
95 goto out;
96
97 /* Enable charger */
98 value = DS1390_TRICKLE_CHARGER_ENABLE;
99 if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
100 value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
101 else
102 value |= DS1390_TRICKLE_CHARGER_DIODE;
103
104 /* Resistor select */
105 switch (ohms) {
106 case 250:
107 value |= DS1390_TRICKLE_CHARGER_250_OHM;
108 break;
109 case 2000:
110 value |= DS1390_TRICKLE_CHARGER_2K_OHM;
111 break;
112 case 4000:
113 value |= DS1390_TRICKLE_CHARGER_4K_OHM;
114 break;
115 default:
116 dev_warn(&spi->dev,
117 "Unsupported ohm value %02ux in dt\n", ohms);
118 return;
119 }
120
121 ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
122
123 out:
124 return;
125 }
126
ds1390_read_time(struct device * dev,struct rtc_time * dt)127 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
128 {
129 struct spi_device *spi = to_spi_device(dev);
130 struct ds1390 *chip = dev_get_drvdata(dev);
131 int status;
132
133 /* build the message */
134 chip->txrx_buf[0] = DS1390_REG_SECONDS;
135
136 /* do the i/o */
137 status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
138 if (status != 0)
139 return status;
140
141 /* The chip sends data in this order:
142 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
143 dt->tm_sec = bcd2bin(chip->txrx_buf[0]);
144 dt->tm_min = bcd2bin(chip->txrx_buf[1]);
145 dt->tm_hour = bcd2bin(chip->txrx_buf[2]);
146 dt->tm_wday = bcd2bin(chip->txrx_buf[3]);
147 dt->tm_mday = bcd2bin(chip->txrx_buf[4]);
148 /* mask off century bit */
149 dt->tm_mon = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
150 /* adjust for century bit */
151 dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
152
153 return 0;
154 }
155
ds1390_set_time(struct device * dev,struct rtc_time * dt)156 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
157 {
158 struct spi_device *spi = to_spi_device(dev);
159 struct ds1390 *chip = dev_get_drvdata(dev);
160
161 /* build the message */
162 chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
163 chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
164 chip->txrx_buf[2] = bin2bcd(dt->tm_min);
165 chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
166 chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
167 chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
168 chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
169 ((dt->tm_year > 99) ? 0x80 : 0x00);
170 chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
171
172 /* do the i/o */
173 return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
174 }
175
176 static const struct rtc_class_ops ds1390_rtc_ops = {
177 .read_time = ds1390_read_time,
178 .set_time = ds1390_set_time,
179 };
180
ds1390_probe(struct spi_device * spi)181 static int ds1390_probe(struct spi_device *spi)
182 {
183 unsigned char tmp;
184 struct ds1390 *chip;
185 int res;
186
187 spi->mode = SPI_MODE_3;
188 spi->bits_per_word = 8;
189 spi_setup(spi);
190
191 chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
192 if (!chip)
193 return -ENOMEM;
194
195 spi_set_drvdata(spi, chip);
196
197 res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
198 if (res != 0) {
199 dev_err(&spi->dev, "unable to read device\n");
200 return res;
201 }
202
203 if (spi->dev.of_node)
204 ds1390_trickle_of_init(spi);
205
206 chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
207 &ds1390_rtc_ops, THIS_MODULE);
208 if (IS_ERR(chip->rtc)) {
209 dev_err(&spi->dev, "unable to register device\n");
210 res = PTR_ERR(chip->rtc);
211 }
212
213 return res;
214 }
215
216 static const struct of_device_id ds1390_of_match[] __maybe_unused = {
217 { .compatible = "dallas,ds1390" },
218 {}
219 };
220 MODULE_DEVICE_TABLE(of, ds1390_of_match);
221
222 static const struct spi_device_id ds1390_spi_ids[] = {
223 { .name = "ds1390" },
224 {}
225 };
226 MODULE_DEVICE_TABLE(spi, ds1390_spi_ids);
227
228 static struct spi_driver ds1390_driver = {
229 .driver = {
230 .name = "rtc-ds1390",
231 .of_match_table = of_match_ptr(ds1390_of_match),
232 },
233 .probe = ds1390_probe,
234 .id_table = ds1390_spi_ids,
235 };
236
237 module_spi_driver(ds1390_driver);
238
239 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
240 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
241 MODULE_LICENSE("GPL");
242 MODULE_ALIAS("spi:rtc-ds1390");
243